Table 2 Characteristics of 39 analyses identifying trial registry entries from cohorts of published articles

Mathieu [59]

234

323

ClinicalTrials.gov, ISRCTN, ICTRP, national register based on country of first author

Outcome reporting bias

2009

Cardiology, rheumatology, gastroenterology

Automatic = 205

Inferred = 6

Inquired = 23

Chowers [105]

49

60

Unknown

Outcome reporting bias

2009

Anti-retroviral therapy

Unknown

Rasmussen [60]

54

137

ClinicalTrials.gov, ISRCTN, ICTRP, NCI-PDQ

To determine association of trial registration with the results and conclusions of published trials

2009

Oncology drugs

Inferred = 54

Kunath [58]

63

106

ICTRP

To observe trial registration in urology journals

2011

Urology

Automatic = 48

Inferred = 15

Ewart [56]

135

124

ISRCTN, ClinicalTrials.gov, ANZCTR, EU-CTR, National Research Register

Outcome reporting bias

2009

RCTs in five high-impact factor journals

Unknown

You [106]

215

366

ClinicalTrials.gov, ISRCTN

Outcome reporting bias

2011

Oncology drugs

Unknown

Reveiz [109]

89

526

ICTRP

Outcome reporting bias

2012

RCT from Latin America and Caribbean

Unknown

Nankervis [108]

37

109

ICTRP

Outcome reporting bias

2012

Eczema treatment

Automatic = 20

Inferred = 17

Pinto [107]

67

200

ClinicalTrials.gov, ISRCTN, ANZCTR, national register based on country of first author

Completeness of clinical trial registration and the extent of selective reporting of outcomes in published trials

2013

Physical therapy

Automatic = 48

Inferred = 2

Inquired = 17

van de Wetering [26]

185

302

ClinicalTrials.gov, ISRCTN, ICTRP, national register based on country of first author

To determine reporting of trial registration numbers in biomedical publications

2012

RCT from core clinical journals

Automatic = 166

Inquired = 19 (contact = 136, responded = 51, published = 19)

Hannink [110]

218

327

ClinicalTrials.gov, ISRCTN, ANZCTR and others

Outcome reporting bias

2013

Surgical interventions

Automatic = 218

Huser [16]

661

698

ClinicalTrials.gov.gov, ISRCTN

Evaluating adherence to ICMJE policy of mandatory and timely clinical trial registration

2013

Trials published in five ICMJE journals

Automatic = 661

Rosenthal [111]

51

55

ClinicalTrials.gov, ISRCTN, ANZCTR, ChiCTR, UMIN

Outcome reporting bias

2013

Surgery

Automatic, inferred, and inquired = unknown

Hopewell [112]

30

69

Unknown

To observe reporting characteristics of non-primary publications of results of RCTs

2013

RCTs from National Library of Medicine’s set of 121 core clinical journals

Automatic = 30

Babu [113]

121

417

Unknown

To observe clinical trial registration in physical therapy journals

2014

Physical therapy journals

Automatic = 121

Lee [114]

8

83

Unknown

Assessment of compliance of randomized controlled trials in trauma surgery with the CONSORT statement

2013

Trauma surgery

Automatic = 8

Li [115]

252

305

ClinicalTrials.gov, Current Controlled Trials, NTR, ANZCTR, UMIN CTR

Outcome reporting bias

2013

Gastroenterology and herpetology

Automatic = 212

Inferred = 40

Norris [116]

50

107

ICTRP

To determine selective outcome reporting

2013

Pharmacotherapy

Automatic = 30

Inferred = 20

Hardt [117]

85

103

ICTRP(ClinicalTrials.gov, ISRCTN, EU-CTR, NTR, ANZCTR, DRKS, JPRNUMIN, ChiCTR, CTRI), Belgian register

To determine whether the results of registered surgical RCTs are published in journals requiring registration

2013

Ten highest rank surgery journals

Automatic = 68

Inferred = 17

Anand [118]

133

197

ClinicalTrials.gov, ISRCTN, ANZCTR

To determine the registration and design alterations of clinical trials in clinical care

2014

RCT in clinical care medicine

Automatic = 105

Inferred = 28

Mann [119]

140

220

ICTRP

To assess the registration status of RCTs and analyse the correspondence of registered outcomes with published outcomes

2014

Clinical geriatrics

Unknown

Walker [120]

75

76

ISRCTN, ClinicalTrials.gov, national register based on country of first author

Outcome reporting bias

2014

RCTs published in British Medical Journal and the Journal of American Medical Association

Automatic and inferred = unknown

Dekkers [121]

29

54

ICTRP

To compare non-inferiority margins defined in study protocols and trial registry records with margins reported in subsequent publications

2015

Non-inferiority trials submitted 2001–2005 to ethics committees in Switzerland and Netherlands

Automatic and inferred = unknown

Østervig [122]

85

200

ISRCTN, IRCT, EU-CTR, ChiCTR, CRiS, UMIN CTR, ClinicalTrials.gov

To check registration of randomized clinical trials

2015

Trials in Acta Anaesthesiologica Scandinavica

Automatic = 85

Scott [62]

160

181

ISRCTN, NTR, ANZCTR, ClinicalTrials.gov, national register based on country of first author

Selective outcome reporting

2015

Psychiatry journals

Automatic = 150

Inferred = 6

Inquired = 4

De Oliveira [123]

107

201

ISRCTN, ClinicalTrials.gov, ICTRP

Outcome reporting bias

2015

Anaesthesiology

Automatic, inferred, and inquired = unknown

Rayhill [61]

58

225

ClinicalTrials.gov and others

To assess the registration status of RCTs and analyse the correspondence of registered outcomes with published outcomes

2015

Core headache medicine journals

Automatic = 58

Dal-Ré [124]

175

178

ClinicalTrials.gov, ISRCTN, ANZCTR, NTR, EU-CTR, CTRI, DRKS

To evaluate adherence to ICMJE policy on prospective trial registration

2016

Trials in high-impact journals

Unknown

Reveiz [125]

52

144

Registered in any international clinical trial registry

To evaluate the influence of trial registration on reporting quality of RCTs

2010

Highest rank journals

Unknown

Rongen [126]

90

362

ClinicalTrials.gov, ISRCTN, ANZCTR, NTR and others

Outcome reporting bias

2016

Orthopedic surgical interventions

Automatic = 90

Harriman [57]

105

108

ClinicalTrials.gov, ISRCTN, ANZCTR, UMIN CTR, NTR, ChiCTR, IRCT

To assess trial registration, analysis of prospective versus retrospective registration

2016

Clinical trials published in the BMC series

Automatic = 105

Inquired = 0

Vera-Badillo [129]

30

164

ClinicalTrials.gov

Outcome reporting bias

2013

Breast cancer

Automatic and inferred = unknown

McGee [128]

74

307

ICTRP

To determine whether trial is registered and declared registration in the publication

2016

Kidney transplantation

Automatic = 44

Inferred = 30

Huić [127]

149

152

ClinicalTrials.gov

To determine completeness and outcome reporting bias

2011

RCTs published in ICMJE journals

Automatic = 149

Chan [34]

519

553

Unknown

Outcome reporting bias

2005

RCTs indexed in PubMed

Inferred and inquired = unknown

Korevaar [130]

52

351

ClinicalTrials.gov, ISRCTN, national register based on country of first author

To identify the proportion of articles for which the corresponding study had been registered

2014

Test accuracy studies

Automatic = 27

Inferred = 11

Inquired = 14 (contact = 324, responded = 187, published = 14)

Jones [131]

57

123

ClinicalTrials.gov, ISRCTN, ICTRP, national register based on country of first author

Outcome reporting bias

2012

Emergency

Automatic = 23

Inferred = 34

Smaïl-Faugeron [132]

73

317

ICTRP

To assess the registration rate of RCTs

2015

Oral health

Automatic = 50

Inferred = 23

Riehm [133]

40

76

ISRCTN, ClinicalTrials.gov, ICTRP

Outcome reporting bias

2015

Psychosomatic and behavioral health

Automatic = 33

Inferred = 7